The present invention relates to a photoelectric conversion element, an imaging device, an optical sensor, and a method of using a photoelectric conversion element.
A conventional optical sensor is an element in which a photodiode (PD) is formed in a semiconductor substrate such as silicon (Si), and as a solid-state imaging device, a planar solid-state imaging device, in which PDs are two-dimensionally arranged and signal charge generated by each PD is read out by a circuit, is widely used.
In order to obtain a color solid-state imaging device, a structure in which color filters that transmit light of a specific wavelength are arranged in a light incident surface of the planar solid-state imaging device is generally used. Currently, a single plate solid-state imaging device, in which color filters that transmit blue (B) light, green (G) light, and red (R) light are regularly arranged on each of the two-dimensionally arranged PDs, is well known and is widely used in a digital camera and the like.
In the single plate solid-state imaging device, the light not transmitted through the color filters is not utilized, and accordingly, light use efficiency is poor. Moreover, in recent years, the number of pixels has been increased, and the pixel size has been reduced. Consequentially, decrease in aperture ratio and decrease in light-collecting efficiency have become problems.
As a solution to the above problems, a structure obtained by forming a photoelectric conversion film formed of amorphous silicon on a substrate for reading out signal is known.
Regarding the photoelectric conversion element, imaging device, and optical sensor using a photoelectric conversion film, several examples of the prior art exist.
For example, JP 2006-100767 A discloses an imaging device using a photoelectric conversion film that uses a quinacridone-based compound.